It worked!!!!!
FJJP, I did it your way (less buttons to press), and now I can send emails again. Many many thanks. Isn't PPRuNe wonderful?
However, that is only part of the problem...though the major part. I still want to stop it disconnecting. What happens is, I have two email addresses, right. So it sends emails, then disconnects. I connect again and it checks for messages on one, then disconnects. I do that again for the second one and it disconnects again. Then I connect again and head for PPRuNe and happily stay there for far too long.
Now, as I'm sure you can understand, this is livable with, but a complete nuisance. And it never used to do it!!!! And the "Hang up when finished" box is definitely not ticked.
Any ideas, you wonderful computer expert people who inhabit this forum (I'm serious; I really do appreciate it).